Would like so me advice on a good shop to diagnose a dead cylinder. Only 500 miles on fresh rebuild from Jorge at European Motorworks. spark is good, fuel delivery is good. compression 115. all other cylinders 145. Since I am sure Jorge will warranty his work I just need a shop to diagnose what happened or likely, cause. then probably have them remove motor, get it over to Jorge for repair, then reinstall and tune. I just dont have time or energy to do it myself anymore.

Willing to transport it anywhere in SoCa, preferable close to Jorge in Hawthorne.

Ok my guess and no this is not a shop that you requested but if the engine runs on carbs the idle jet port is clogged

Better diagnosis needed at this point.

Check carb/FI stuff first.

115 is NOT a dead cylinder. It's a cylinder that hasn't fired properly in a while.

Bunch of diag before compression and leak downs.

Intake valve adjustment is CRITICAL for equal number compression tests...

I'd recheck valve clearance at 500 miles on one of these anyway.

This might be "super critical" if you changed up and are using chromoly push rods.

Those puppies spec out 0 valve clearance cold and if you've had any "wear in" at all your clearances might be too tight now.

I don't think that needs to come out yet...

was it running good for the first 500 miles?

You guys are awesome. Yes, It ran GREAT for first 500. Pulled like a champ. then, started sputtering on accelaration. Just a small hiccup, then got worse and just really wouldnt pull. idle rpm dropped.

I cleaned jets, but NOT the idle jets. So thats interesting. but sitting at idle, i pulled plug wires one at a time and there is not change in idle when I pull number 3. plug looked clean and gray

I agree it needs proper diagnosis.

The dreaded number 3!

If you were getting fuel and the cylinder was not firing (from some other malady) the plug would look wet...

I bet mb911 has it right!

That's also stupid easy to check...

This one is throwing me a curve ball. I can see the engine not running good with a carb jet clogged, but how can the compression be lower due to a carb issue?

everything gets "dry"

It's common to see an engine that has been stored for a long time have lousy compression and leak down tests.

compression usually comes right back after a complete drive cycle.

Come to temperature, operated under load, allow to cool...



Intake valve adjustment has the biggest effect on compression if it is out of range.

The adjustment controls when the intake valve closes which is ALWAYS after the piston has hit BDC on the intake stroke and is traveling UP the bore.

Tight adjustment means it closes later (or never).

Later closing equals lower compression readings from a gauge.

I'd recheck valve adjustment after 500 miles on a T4 as preventative maintenance.


Before I rechecked this (and I would) I'd put money on mb911's diag...

@MB911 HUGE THANK YOU. havent road tested it yet, but huge difference! runs beautifully, holds idle again, and obvious difference when removing each plug wire.

thank you ALL

That’s great news

Thats good news.

Yes that first valve adjustment is critical. I did mine around 600 miles. You have to expect the adjustment to change on a new engine as it breaks in.

Zach

call rich bontempe at high performance house

Good news that you got the fuel delivery and valve adjustment issues resolved!

One more thing (that can cause problems with compression in a new motor). It's a really good idea to go through the documented procedures for breaking in/setting the rings. If not done or done improperly the rings won't seal right. Improves your engine's longevity.